Electromechanical relay

ABSTRACT

An improved relay incorporating a cantilever comprised of an elongated piezoelectric element joined to an electrical conductive armature with the armature portion of the cantilever positioned about contact means whereby the electrical circuit relationship is responsive to deflections in said piezoelectric element.

O Umted States Patent 1 1 3,777,093

Stems et a]. Dec. 4, 1973 [54] ELECTROMECHANICAL RELAY 2,166,763 7/1939 Mason 317/144 3,014,104 12/1961 Cobine et al. 337/109 X [76] hvemors- 57 g i g zfi 2,183,708 12 1939 Cummings et a] 317 144 x ay, an ose, a1 Francis Anthony Sutter, 77 31 FOREIGN PATENTS OR APPLICATIONS Rambow San Cahf- 95129 1,096,824 12/1967 Great Britain 200/181 [22] Filed: May 25, 1972 [21] APPL N0I 257,053 Primary Examiner Herman J, Hohauser Assistant Examiner-Robert A. Vanderhye Related Apphcanon Dam Attorney-Thomas E. Schatzel [63] Continuation of Ser. No. 82,361, Oct. 20, 1970,

abandoned.

- [57] ABSTRACT [52] US. Cl 200/181, 317/144, 337/109,

337/109 An Improved relay incorporatmg a cantIlever com- [51] Cl Holh 59/00 prised of an elongated piezoelectric element joined to [58] Field 317/144 an electrical conductive armature with the armature portion of the cantilever positioned about contact [56] References Cited means whereby the electrical circuit relationship is re- UNITED STATES PATENTS sponsive to deflections in said piezoelectric element. 3,501,745 5 Claims, 12 Drawing Figures 3/1970 Beckman 317/144 X ELECTROMECHANICAL RELAY This is a continuation, of application, Ser. No. 82,361 filed Oct. 20, 1970, now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to electromechanical relays and more particularly to a relay employing a pi- 'e'z oelectric element. Piezoelectric materials respond physically to the application of a driving voltage and become deformedfAn elongated element of piezoelectric material responds by bending. The element is approximately polarized so that application of a suitable voltage to the crystals results in expansion along one axis and contraction along another axis such that the element flexs or bends. Thus, an armature joined to the element may be actuated to pivot relative to a plurality of positioned contacts responsive to physical deflections in the element.

Piezoelectric relays possess a high degree of electromechanical efficiency relevant to that of electromagnetic relays. Piezoelectric relays do not require windings or iron cores. Power requirements for excitation are small. The characteristics of piezoelectric'elements are capacitive in nature. Thus, they may be operated by a small drive current building up a charge over a comparatively long period or by a larger current applied over a short period. After the drive potential is removed, the relay will return to its normal position after a time delay. The time delay depends on the time constant of the crystal. The delay can be controlled dependant on the characteristics of the crystal and incorporation of external resistance or shorting bars.

The prior art includes piezoelectric and electrostrictive relays. U.S. Pat. No. 3,292,111 issued to M. B. Cotton discloses an electrostrictive relay including a longitudinal bimorph or inultimorph element. U.S. Pat. No. 3,430,020 issued to R. Von Tomkovitch, et al., discloses a piezoelectric relay including a piezoelectric material forming a pair of pressure chambers.

Piezoelectric relays heretofore available are relatively complex in structures. Such structures are costly to manufacture and maintain. Further, the reliability of prior art structures is substantially decreased under adverse atmospheres, for example varying temperatures, vibrations, etc.

SUMMARY OF THE PRESENT INVENTION The present invention teaches a relay of simplified structure and highly reliable operation.

An exemplary embodiment includes a housing with an elongated cantilever comprised of a piezoelectric element and armature contactor positioned within the chamber formed by the housing. One end of the cantilever is anchored and the other end is suspended. Intermediate the element and contactor is an insulator interlink. Terminal means are positioned adjacent to the armature. The terminals electrically extend to the exterior of the housing. When electrically energized, the element deflects in a bending mode generating lateral movement. The armature in turn responds laterally to the bending or flexure of the crystal and the position of the armature relative to the terminals is in turn controlled.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective, partially sectioned view of a relay incorporating the teachings of the present invention;

FIG. 1A is a cross-sectional view of the relay of FIG. 1 taken along theline 1A 1A;

FIG. 1B is a cross-sectional view of the relay of FIG. 1 taken along the line 18 1B of FIG. 1;

FIG. 1C is an end view of an alternative embodiment of an armature incorporated in the relay of FIGS. 1 18;

FIG. 2 is a perspective, partially sectioned view of an alternative embodiment of the present invention;

FIG. 2A is a cross-sectional view of the relay of FIG. 2 taken along the line 2A 2A;

FIG. 2B is a cross-sectional view of the relay of FIG. 2 taken along the line 2B 28;

FIG. 2C is a cross-sectional view of the relay of FIG. 2 taken along the line 2C -2C;

FIG. 3 is a perspective, partially sectioned view of an alternate embodiment of the present invention;

FIG. 3A is a cross-sectional view of the relay of FIG. 3 taken along the line 3A 3A;

FIG. 3B is a cross-sectional view of the relay of FIG. 3 taken along the line 33 3B; and

FIG. 3C is a cross-sectional view of the relay of FIG. 3 taken along the line 3C 3C.

DESCRIPTION OF PREFERRED EMBODIMENTS FIGS. 1, IA and 1B illustrate a relay, referred to by the general reference character 1 and incorporating the teachings of the present invention. The relay is comprised of a non-conductive dielectric housing having a mechanically rigid base support member 3 and a cover 5. The base support member 3 is in the shape of a flat rectangular member having a ridge 7 extending about the periphery. The cover 5, in cross-section, is of inverted U-shape with a ridge 9 adapted to compliment the ridge 7 of the base support. Accordingly, with the cover 5 positioned about the base support 3 with the ridges 7 and 9 in engagement, an internal chamber 11 is formed. The base support 3 and cover 5 are comprised of an insulative material. Dielectric materials comprised of a glass filled thermo plastic or thermoset material have proven desirable.

Protruding through the base support member 3 are a pair of input electrical power terminals 13 and 14. The terminals 13 and 14 are anchored within the base support member and protrude to the exterior to receive input electrical drive signals. Within the interior the terminals 13 and 14 are each bent at an approximate angle to establish an arm 15 and 16 respectively having an axis substantially parallel with the longitudinal axis of the chamber 11. Within the chamber 11 the arms 15 and 16 are secured to opposing surfaces of an elongated flat rectangular piezoelectric bimorph crystal 17. The crystal 17 is mounted as a cantilever I7 and mechanically supported about one terminal end by the input terminals 13 and 14 while the opposite terminal end is suspended. The power terminal 13 and arm 15 are secured to one surface of the crystal by means of a silver solder 18 while the terminal 14 and arm 16 are secured to the opposing surface of the crystal by means of a silver solder 19. The crystal 17 is secured at its opposite end to an insulative interlink 20. The interlink 20 and end of the crystal 17 are thus suspended. The insulative interlink 20 is of oblong shape and of a thickness exceeding that of the crystal.

The base support 3 anchors a plurality of output signal contact posts 21, 23 and 25. The post 21 is positioned adjacent to the interlink 20. The posts 23 and 25 are longitudinally displaced relative to the terminal 21 within the chamber. The posts 23 and 25 are positioned laterally relative to one another and in the travel path of the armature.

An armature wire 27 is secured about the post 21 by means of a solder or weld. The wire extends to an elongated armature contactor 29. The armature 29 extends longitudinally parallel to the longitudinal axis within the chamber 11 and the crystal 17. One terminal end of the armature 29 is embedded within the insulative interlink 20 and is in electrical engagement with the contactor 29 by means of the wire 27 which may be soldered or welded thereto. The opposing terminal end of the armature 29 extends beyond the terminal posts 23 and 25 intermediate thereof.

The crystal element 17 of the relay 1 is in the form of a piezoelectri bimorph element. The dimensions of the element may be in the order of approximately 0.020 inches (20 mils) in depth; 0.100 inch in width and 0.5 inches in length. The element 17 may include two flat crystal segments 17a and 17b of barium titanate with a shim plate 170 of brass sandwiched intermediate. Intermediate the crystal plates and the brass plates is layer of nickel spheres embedded in epoxy (not shown). The power terminals 13 and 14 are connected across the two crystal plates 17a and 17b as illustrated in FIG. 1B to form a series connection of the crystals. Though not shown, electrical connection of the terminal 13 to the brass shim 17c and electrical connection of the terminal 14 to both of the crystals provides a parallel connection of the piezoelectric element. When electrical signals are applied across the power input terminals 13 and 14 the element 17 becomes electrically energized. As shown, the element 17 s serially energized with the active plates oppositely polarized. The drive signals give rise to oppositely directed transverse strains in the piezoelectric element which gives rise to bending or deflecting of the free end of the element. The element 17 tends to pivot about the terminal ends of the arms and 16. The insulative interlink 19 also pivots responsive to the element 17. The armature contactor 29 acts as an extension of the element 17 through the interlink 19. Consequently, the movement of the armature 29 is an amplification of the movement of the crystal as a result of the longer moment arm established by the interlink and armature contactor.

- The armature may be in the form of a 20 mil diameter cylinder. The terminal posts may be in the order of 20-25 mils in diameter and spaced apart to leave approximately one mi] spacing between the normally open post and armature when the relay is not activated.

When the piezoelectirc element 17 is at rest, the armature 29 rests against the electrical contact 23 to provide a normally closed condition between the terminals 21 and 23. When the element 17 is energized, it flexs laterally relative to the base 3. The flexure causes the armature 29 to move away from the terminal 23 towards the terminal 25. The rotational velocity of the armature imparts a mechanical force to the armature such that when it comes into physical contact with the terminal 25, good electrical contact is made to complete the circuit between the terminals 21 and 25. This action is of a form C" set of relay contacts. A form A set of contacts may be made by eliminating the terminal 23.

FIG. 1C illustrates an alternative embodiment of the relay 1 in which an auxiliary permanent magnetic field is incorporated. Such a structure may be used in environments where it is not essential that the relay be nonresponsive to impinging magnetic fields or free of generating magnetic fields. For example, the structure 1 of FIGS. 1-1B may be modified to incorporate an armature 29' having a polarized permanent magnet 29a embedded within a magnetic cylinder 29'b. The magnetic field of the magnet 29a tends to increase the force on the armature 29 in the direction of the closest contact pole piece 23 or 25', which are also of a magnetic material. The magnetic attraction tends to increase the contact pressure and thereby increase the current handling capacity of the contact. Preferably, the force due to the magnetic field is set to less than the relaxation force of the crystal once the drive signal is removed from the crystal. This will permit the armature to return to the normal position.

FIGS. 2, 2A, 2B and 2C represent an alternative embodiment of the present invention, referred to by the general reference character 50. The relay 50 include a bimorph piezoelectric element 52 similar to the element 17, positioned horizontally within a housing such that it flexes in a vertical plane. The housing includes a molded base support 54 and a molded cover 56. The base support member 54 is in the shape of a flat rectangular member with a pair of exterior clearing ridges 57 and 58 and an interior attachment shoulder 60. The cover 56, in cross-section, is of an inverted U-shape and receives the base support 54 about the interior surface of the outer edge. Accordingly, with the cover 56 positioned about the base support 54 an internal chamber 62 is formed. The base support 54 and cover 56. are comprised of an insulative material, e.g. dielectric material comprised of a glass filled thermoplastic or thermoset material.

Protruding through the base support member 54 are a pair of input power terminals 64 and 66 in the form of terminal posts extending from within the chamber to the exterior. Within the chamber 62 the posts 64 and 66 are joined to a lead wire 68 and 70, respectively, soldered or welded to opposite crystals of the element 52. The element 52 is anchored to the attachment shoulder 60. The opposite end of the element 52 is engaged to an insulative interlink 72 similar to the interlink 19 of the relay 1.

The interlink 72 is also secured to an armature contactor 74 which acts as an extension of the element. The armature 74 is electrically engaged to a lead wire 76 embedded within the interlink 72. The opposite end of the lead wire 76 is secured to a terminal post 78 extending to the exterior.

About the end of the armature 74 are a pair of L- shaped contact posts 80 and 82 with the post 82 overlapping the post 80. Intermediate the overlaps is a spacing through which the armature 74 extends. The posts 80 and 82 extend to the exterior of the housing for connection to external circuitry. As illustrated, the posts 64, 66, 78, 80 and 82 may each carry a shoulder 83 embedded within the base 54 to provide physical support of the terminals.

, Accordingly, upon application of an input power signal across the input terminals 64 and 66, the element 52 flexes in a vertical plane such that the armature 74 is moved in a vertical path intermediate the overlap portions of the posts 80 and 82. The housing carries an evacuation portal 84 which may be sealed by means of a seal 86 after the chamber 62 is evacuated and filled with a dry gas. During construction, after the relay 50 is assembled with the cover 56 and base 54 sealed in place, the chamber 62 may be evacuated through the portal 84 to rid the chamber of contaminants and moisture. The chamber 62 may then be filled with a dry gas, e.g. nitrogen, and the portal 62 sealed with the sealant 86. The dry gas tends to eliminate further moisture from entering the chamber which may otherwise tend to condense on the interior surface.

FIGS. 3-3C illustrate a further embodiment of the present invention, referred to by the general reference character 100. The relay includes a cylindrical housing 102 comprised of an insulative dielectric material. A pair of end caps 104 and 106 are secured about opposite terminal ends of cylinder 102 to form an internal chamber 108. Protruding from the chamber 108 to the exterior through the cap 106 are a pair of power input terminal posts 110 and 112. The posts 110 and 112 are embedded within the cap 106. Protruding from the chamber 108 to the exterior through the cap 104 are a pair of signal output lead terminal posts 114 and 116. The posts 114 and 116 are embedded within the cap 104.

The power input post 112 is secured to one end of a flat rectangular bimorph piezoelectric element 118 so as to provide structural support for said crystal. The post 112 simultaneously makes electrical engagement with the outer surface of the crystal 118. The element 118 extends longitudinally within the chamber 108 and is secured about its opposite end to an insulative interlink 120. The interlink 120 in turn is engaged to an armature contactor 122 so as to establish a crystalinterlink-armature cantilever within the chamber 108. The piezoelectric element 118 is engaged to a L-shaped insulative support 124 with one leg extending longitudinally within the chamber and in parallel with the element 118 and armature 122. The other leg of the support 124 is adhered to the element 124 by means of a weld 126 such that the element 118 is sandwiched intermediate the post 112 and the support 124. The element 118 is electrically engaged to power terminal 110 by means of a lead wire 125. The terminal end of the long leg of the support 124 is engaged to a contact 128 positioned laterally opposite to the armature 122. The contact 128 is secured to said support 124 by means of a weld 130. A lead wire 132 is soldered to the armature contactor 122 and to the terminal post 114. Also, the contact 128 is soldered to a lead wire 134 engaged to the terminal post 116.

In operation, application of a power signal across the input posts 110 and 112 results in flexure of the piezoelectric element 118 in a vertical path such that the crystal-interlink-armature flexes vertically. Thus, the contactor 122 is moved in and out of contact with the terminal contact 128 thereby controlling the electrical circuit intermediate the signal posts 114 and 116. It may be noted in the structure 100 that the support structure 124 and contact 128 are suspended as is the crystal-interlink-armature chain. Thus, the support 124 and chain are equally subjected to vibration and shocks. Accordingly, the electrical operation of the relay is relatively stable in vibrating atmospheres.

Relay structures incorporating the teachings of the present invention require low actuating energy to operate. The actuating energy may be in the order of one microJoule per contact set. The input inpedance may be in the order of 1,000 megohms shunted by approximately 10 farads. The turnoff time is dependant upon the time constant of the piezoelectric and any resistance added about the input power terminals. Accordingly, the turnoff time delay may be controlled according to the specific application of the relay. lf during operation, input power is momentarily lost, the switches may hold their position for a time duration dependant upon the time constant. The relay may be made of extremely small size. The relay does not generate any substantial heat and may be made relatively free of the effects of impinging magnetic fields. Relays according to the present invention have wide application in environments where low power switching is required; in environments with space limitations, such as in portable and battery operated equipment; and in environments where isolation between input and controlled circuitry is desired.

We claim:

1. An electromechanical relay comprising, in combination:

a housing forming an enclosed internal chamber, the housing having two endwalls and sidewalls, said sidewalls extending longitudinally of and interconnecting said endwalls to form said enclosed internal chamber;

an elongated rectangular-shaped piezo-electric element positioned internally within the enclosed chamber and extending longitudinally within said chamber substantially parallel to said sidewalls, the element being flexible laterally intermediate said sidewalls responsive to electrical power applied to the element;

support means for anchoring a first longitudinal terminal end of the element to the housing within the internal chamber and adjacent to one of said endwalls, the other longitudinal terminal end of the element being suspended within the enclosed internal chamber;

input terminal means embedded within the housing walls and protruding through the housing to within said internal chamber and externally to the exterior of the housing, the input terminal means being positioned externally to receive input electrical power from an external source, the input terminal means being electrically connected internally to the element adjacent to said first longitudinal terminal end;

an elongated electrically insulative interlink having a thickness greater than the thickness of the element, the interlink being anchored about one of its longitudinal terminal ends to said other longitudinal terminal end of the element, the interlink extending longitudinally within the chamber in tandem longitudinal alignment with said element and substantially parallel with said sidewalls, the interlink establishing an elongated moment arm with the element;

an elongated electrically conductive armature contactor having one longitudinal terminal end anchored within and adjacent the other longitudinal end of the insulative interlink, extending longitudinally in tandem longitudinal alignment with the interlink substantially parallel with said sidewalls, the interlink electrically insulating the element from the armature contactor, the armature contactor establishing an elongated moment arm with the interlink and the element; and a plurality of contact terminals embedded within said housing walls and protruding through said housing walls to within said internal chamber and externally of the housing, the contact terminals projecting internally to a position laterally adjacent to the armature contactor, at least two of said contact terminals being offset relative to one another within the chamber, a flexible conductive wire connected to one of said contact terminals within the chamber and about its other end to said conductive armature contactor. 2. The relay of claim 1, further including an elongated insulative support within the chamber and substantially parallel with the element, one terminal end of said support being suspended within the chamber and positioned adjacent to said armature contactor, and a contact member engaged to said support about the suspended end of said support adjacent to the armature contactor.

3. The relay of claim 1 in which the insulative support is L-shaped with the terminus of one leg joined to the element and the terminus of the other leg being suspending and engaged to said contact.

4. The relay of claim 1 further including permanent magnetic field means embedded within the armature contactor for establishing a magnetic field intermediate the armature contactor and the contact means.

5. The relay of claim 4 in which the armature contactor and the contact tenninal means comprise a magnetic material. 

1. An electromechanical relay comprising, in combination: a housing forming an enclosed internal chamber, the housing having two endwalls and sidewalls, said sidewalls extending longitudinally of and interconnecting said endwalls to form said enclosed internal chamber; an elongated rectangular-shaped piezo-electric element positioned internally within the enclosed chamber and extending longitudinally within said chamber substantially parallel to said sidewalls, the element being flexible laterally intermediate said sidewalls responsive to electrical power applied to the element; support means for anchoring a first longitudinal terminal end of the element to the housing within the internal chaMber and adjacent to one of said endwalls, the other longitudinal terminal end of the element being suspended within the enclosed internal chamber; input terminal means embedded within the housing walls and protruding through the housing to within said internal chamber and externally to the exterior of the housing, the input terminal means being positioned externally to receive input electrical power from an external source, the input terminal means being electrically connected internally to the element adjacent to said first longitudinal terminal end; an elongated electrically insulative interlink having a thickness greater than the thickness of the element, the interlink being anchored about one of its longitudinal terminal ends to said other longitudinal terminal end of the element, the interlink extending longitudinally within the chamber in tandem longitudinal alignment with said element and substantially parallel with said sidewalls, the interlink establishing an elongated moment arm with the element; an elongated electrically conductive armature contactor having one longitudinal terminal end anchored within and adjacent the other longitudinal end of the insulative interlink, extending longitudinally in tandem longitudinal alignment with the interlink substantially parallel with said sidewalls, the interlink electrically insulating the element from the armature contactor, the armature contactor establishing an elongated moment arm with the interlink and the element; and a plurality of contact terminals embedded within said housing walls and protruding through said housing walls to within said internal chamber and externally of the housing, the contact terminals projecting internally to a position laterally adjacent to the armature contactor, at least two of said contact terminals being offset relative to one another within the chamber, a flexible conductive wire connected to one of said contact terminals within the chamber and about its other end to said conductive armature contactor.
 2. The relay of claim 1, further including an elongated insulative support within the chamber and substantially parallel with the element, one terminal end of said support being suspended within the chamber and positioned adjacent to said armature contactor, and a contact member engaged to said support about the suspended end of said support adjacent to the armature contactor.
 3. The relay of claim 1 in which the insulative support is L-shaped with the terminus of one leg joined to the element and the terminus of the other leg being suspending and engaged to said contact.
 4. The relay of claim 1 further including permanent magnetic field means embedded within the armature contactor for establishing a magnetic field intermediate the armature contactor and the contact means.
 5. The relay of claim 4 in which the armature contactor and the contact terminal means comprise a magnetic material. 